Proximity-based services may be provided between two user equipments (UEs) having proximity service capabilities, and could be utilized for a variety of purposes. Such purposes could include public safety services, for example for providing various law enforcement officers or other public safety officers notice that other officers are in close proximity, relaying information between safety officers who are out of network coverage, retransmitting a safety officer's communications where the safety officer is out of coverage but the D2D UE is within network coverage, among others.
Non-public safety services may also be accommodated by D2D communications. These may include, for example, social media where two friends are in close proximity to each other and the UEs can communicate directly with each other, for providing services such as a UE in an automobile and a smart meter dealing directly with each other to help a driver find a parking spot, among other scenarios. Such use cases are, for example, described in the 3rd Generation Partnership Project (3GPP) Technical Report (TR) 22.803, “3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Feasibility Study for Proximity Services (proSe) (Release 12)” v12.1.0, March, 2013, the entire contents of which are incorporated herein by reference.
In order to utilize the D2D communication, proximity discovery may be used to identify potential UEs that are within close proximity to the UE desiring D2D communication. An efficient mechanism for proximity discovery is therefore desirable.